This application claims benefit of Japanese Applications No. 2000-099330 filed in Japan on Mar. 31, 2000 and No. 2000-099331 filed in Japan on Mar. 31, 2000, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a lens barrel which has a plurality of lens frames which are relatively movable in forward and backward directions.
2. Related Art Statement
In a conventional lens barrel having a lens frame which is able to move in forward and backward directions, generally, a mechanism which combines a cam groove which is slanted with respect to the optical axis and a cam follower which is fit into the cam groove so as to be freely slidable, has been used as a mechanism for driving the cylindrical lens frame in forward and backward directions. Conventionally, a structure in which the entire slide face of the cam follower is driven to merely slide on a cam slide face has been used as the sliding mechanism for the cam follower which is fit in the cam groove.
However, lens barrels have become smaller due to demands in recent years to make products smaller and more light-weight. Further, there has been the trend to make the thickness of the built-in lens frame smaller. Thus, the lens frame itself has come to be easily deformable. In lens barrels having the above-described conventional structure, when a force greater than needed was applied to the cam follower, there was the concern that the lens frame would deform and the cam and the cam follower would disengage.
On the other hand, in the structure for fixing the above-described conventional cam follower at the lens frame, a fixing structure was used in which a straight shaft portion of the cam follower was press-fit into a fixing hole of the lens frame.
The size of the lens frame has become smaller due to demands in recent years to make products more compact and more light-weight, and there has been the trend to make the lens frame thinner as well. Accordingly, in the above-described cam follower fixing structure, the dimensions of the shaft portion of the cam follower press-fit into the lens frame were also made extremely small. Thus, in cases in which a force greater than needed was applied to the cam follower, there was the fear that the shaft portion which was press-fit in would come out or would be unsteady. Note that there are problems, in terms of the production process and in terms of product management, in using an adhesive in the fixing of the shaft portion, and thus, it is difficult to use an adhesive in practice.
The present invention was devised in order to overcome the above-described problems, and an object of the present invention is to provide a lens barrel having a mechanism for moving a frame forward and backward to which a cam follower is applied, wherein it is difficult for a sliding fit-together portion of the cam follower to come out of place, wherein it is difficult for offset to arise at the portion of the cam follower fixed to the lens frame, wherein the frame can be made more compact, and wherein smooth driving in forward and backward directions is made possible.
One lens barrel of the present invention has a first frame having a cam groove which includes a slide face; a second frame which moves relative to the first frame; and a cam follower, provided at the second frame and having a cam follower slide face which slides on the slide face of the cam groove, the cam follower having, on the cam follower slide face, at least two edges for biting-into the slide face of the cam groove. When the cam follower attempts to tilt, the edges bite into the cam follower slide face of the cam groove, such that the fit-together state therebetween is prevented from coming out of place.
Another lens barrel of the present invention has a frame member having a hole; and a cam follower having a shaft portion which is fit together with and mounted to the hole of the frame member, wherein a plurality of edges are formed at a surface of a fit-together portion of the shaft portion which is fit together with the hole. In a state in which the shaft portion is fit together with the hole, the edges bite into the hole, so as to prevent the cam follower from being offset from the frame member.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.